Trichlorosilane (SiHCl3, boiling point 31.8° C.), which is a liquid material at room temperature, for example, along with tetrachlorosilane (SiCl4, boiling point 57.6° C.) and germanium tetrachloride (GeCl4, boiling point 84° C.), is useful in a manufacturing process of a silicon epitaxial wafer, an associated integrated device or the like and is typically gasified for practical use.
In the manufacturing process, one type of trichlorosilane consumption facility includes raw gas introduction means, a heat source such as an infrared lamp, a quartz glass reaction container insulated from the outside air, and gas discharge means.
The reaction container includes a carbon susceptor coated with SiC, and a silicon wafer is placed on the susceptor. The silicon wafer and the susceptor are increased in temperature to a predetermined temperature using the external heat source such as the infrared lamp and are then maintained.
Trichlorosilane is gasified beforehand, and passes over the surface of the silicon wafer on the carbon susceptor, which is maintained at a high temperature and rotates, along with hydrogen gas as a carrier gas and a dopant gas to control specific resistance. At this time, a new silicon layer is formed on the silicon wafer due to a thermal decomposition reaction and a hydrogen reduction reaction. This is a so-called “silicon epitaxial wafer,” and is widely used for many silicon devices including an IC.
As one of useful vaporization methods of trichlorosilane that is liquid at room temperature, there is a continuous distillation-type trichlorosilane vaporization supply apparatus including: an evaporator for vaporizing liquid trichlorosilane; a condenser disposed immediately above the evaporator and connected to the evaporator via a connection portion provided with a gate valve; and a controller and a pressure reducer that allows a set pressure and an apparatus internal pressure to be equal to each other, in which the pressure reducer performs a pressure adjusting operation in an electrical manner under instruction of the controller, the condenser has a sufficient heat exchange area to condense substantially the total amount of supersaturated trichlorosilane, the evaporator vaporizes a greater amount of trichlorosilane than a necessary amount for a silicon epitaxial growth apparatus in a state in which the gate valve is open, the vaporized trichlorosilane is fed to the condenser through the connection portion, the condenser condenses substantially the total amount of the supersaturated trichlorosilane, and the condensed trichlorosilane is returned to the evaporator through the connection portion by gravity.
However, the above-described continuous distillation-type trichlorosilane vaporization supply apparatus has high energy loss. More specifically, in the condenser section included in the continuous distillation-type trichlorosilane vaporization supply apparatus, the condensed and liquefied trichlorosilane liquid at a low temperature drops on the evaporator positioned immediately therebelow, and thus the temperature of the trichlorosilane liquid in the evaporator is instantly reduced.
When the temperature of the trichlorosilane liquid in the evaporator is significantly reduced, a needed amount of vaporized trichlorosilane may not be reached, and this causes a reduction in the concentration of trichlorosilane-hydrogen mixed gas. Therefore, there is concern of a reduction in the growth rate of a silicon epitaxial layer or a reduction in specific resistance.
To avoid this, the vaporized amount of trichlorosilane has to be ensured by increasing the thermal capacity and minimizing the decrease in temperature by increasing the temperature of the trichlorosilane liquid in the evaporator to a higher temperature than needed or increasing the capacity of the evaporator.
However, although increasing the temperature of the trichlorosilane in the evaporator generally leads to an increase in the vaporized amount and thus prevents insufficiency in the vaporized amount, there is a need to increase the ability of the condenser and a heat transfer area at the same time. This causes an increase in the capacity of the evaporator, an increase in the size of the apparatus, and an increase in cost. Moreover, depending on the size, strict regulations may be applied by law (Fire Service Act for hazardous materials, Industrial Safety and Health Act for pressure containers), and this requires further increase in expenditure for surrounding facilities and the like.
It could therefore be helpful to provide an apparatus that
1) reduces facility costs or running costs, and
2) is not or slightly regulated by law
by reducing the size further than in the above-described apparatus in the related art having the same ability.